Positron Emission Tomography (PET) is a nuclear imaging technology that makes use of a range of positron-labeled tracers to provide images that reflect different parameters relevant to tumor biology. PET technology is now playing a prominent and an increasingly visible role in modern cancer research and clinical diagnosis. However, there is urgent need for improvement in PET instrumentation in order to exploit the full potential of this promising technique. The performance of current PET systems is limited by the available detector technology. Scintillation crystals coupled to photomultiplier tubes are commonly used as detectors in PET systems. Important requirements for the scintillation crystals used in PET systems include fast response, high sensitivity, high light output, high energy and timing resolution, and low cost. None of the established scintillators meet all these requirements. The goal of the proposed project is to explore a new scintillator that has the potential to provide ultra-fast response, high gamma ray stopping efficiency, and very high light output. Successful completion of the proposed effort would create exceptional opportunities for PET imaging including time-of-flight PET studies. Commercial Potential: PET, SPECT, CT, radiology, high energy and nuclear physics, X-ray diffraction, Non-destructive evaluation, nuclear non-proliferation, and geological exploration.